ML19319B752

RO NP-33-77-44:on 770729,indication Variation on Level transmitters,LT-SP9A6 & LT-SP9A7,found Greater than Allowed. Caused by Leaking Vent Valves in Transmitter.Valves Tightened & Level Indication Returned to Normal

ML19319B752
Person / Time
Site:	Davis Besse
Issue date:	08/23/1977
From:	George T, Lingenfelter J TOLEDO EDISON CO.
To:
Shared Package
ML19319B643	List: ML19319B642 ML19319B752
References
NUDOCS 8001270213
Download: ML19319B752 (2)

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@DI Indication variati.pn on two Steam Generator level transmitters (LT-SP9A6I 7 89 , .c

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TOLEDO EDISON COMPANY DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLEMENTAL INFORMATION FOR LER NP-33-77-44 DATE OF EVENT: July 29, 1977 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Indication variation on two Stean Generator level transmitters (LT-SP9A6 and LT-SP9A7) was greater than the allowed differential tolerance of 10 inches Conditions Prior to Occurrence: The plant was in Mode 3, with Power (MWT) = 0 and Load (MRE) = 0.

Description of Occurrence: At 0930 hours0.0108 days <br />0.258 hours <br />0.00154 weeks <br />3.53865e-4 months <br /> on July 29, 1977, Instru=ent and Control personnel were calibrating and repairing tubing leaks on one Steam Generator level transmitter at a ti=e (LT-SP9A6, 9A7 and 9B9). Each transmitter was restored to service uithin 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. At 1045 hours0.0121 days <br />0.29 hours <br />0.00173 weeks <br />3.976225e-4 months <br /> while performing ST 5099.01, Miscellanecus Instrument Shift Checks, 2 Steam Generator level transmitter india.ations on s LT-SP9A6 and LT-SP9A7 were greater than the allowed differential colerance of 10

) inches. This placed the unit in the Action Statement of Technical Specification d 3.3.2.2.(b).

Designation of Aeoarent Cause of Occurrence: After a Maintenance Work Order was issued, it was discovered that the "ent valves on the transmitter body were leaking causing a loss of level indication in the Contrrl Room. The vent valves were never properly tightened during the calibration.

l Analysis of Occurrence: Since (he indications never went out of the tolerance that would require a manual trip of the Steam and Feedwater Rupture Control Systa:

Channel, the Channel re=ained operable and there was no threat to the health and safety of the public or Station personnel.

Corrective Action: SFRCS level indicators were monitored closely to determine if any of the channels must be tripped as per Action Statement #13 of Table 3.3-11.

The vent valves were tightened to stop the leaks and Steam Generator level indica-tion was returned to normal. Investigation of this problem is continuing with the vendor (Rosemont).

Failure Data: Stes: Generator level was inoperable on one prior event (NF-33-7 7-21) ,

} but the cause of the event was a deficient design in the power supplies.

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